Background: Denture cleansing agents which most found in the market known as sodium hypochloride. However, the sodium hypochloride has some negative effects to the denture base, obiter: can cause the whitening effect to the denture base, decrease the transversal strength of the denture base, and change the surface structure of the denture base. Much research was done to find a natural denture cleaning agents which have antifungal properties, one of them is the mangosteen peel extract with a concentration of 50%. Mangosteen peel extract contains xanthones, flavonoid, saponin, and tannin that have antifungal properties. Mangosteen peel extract also contains tannin, xanthones, and anthosianin that contain color pigments. Purpose: to determine the effect of mangosteen peel extract as a denture cleanser against discoloration on acrylic plate. This type of research is an experimental laboratory. Methods: in this study using a sample of heat cured acrylic resin color clear (transparent) with a round shape diameter 15 mm thickness 2 mm by 42 pieces, divided into six groups. The control group by soaking the samples in sterile distilled water for each 4 days, 12 days and 20 days. The treatment group by soaking the samples in the mangosteen peel extract for each of 4 days, 12 days and 20 days. Firstly, the entire sample was soaked in sterile distilled water for 2 x 24 hours, then soaked appropriate control and treatment groups. After completion of the immersion, the samples were dried and measured value of the color change with a series of tools optic spectrophotometer. Results:discoloration occurs on acrylic plate sample immersion in mangosteen peel extract 50%. From the test results Independent T Test between each control and treatment groups 4 days, 12 days, and 20 days found significant color change (p <0.05). Conclusion: there is a discoloration of heat cured acrylic resin immersion in liquid mangosteen peel extract 50%. The color change caused have significant value in the group of immersion for 4 days, 12 days, and 20 days with the highest discoloration in the group of 20-day immersion